A recent study on ArXiv challenges the reliability of the so-called "direct wave," a component of gravitational radiation emitted after black hole mergers, as an indicator of the event horizon properties of the remnant black hole. Previous research had associated the frequency and damping time of this wave with horizon characteristics, and it had even been used to test Hawking's area law.

However, the new analysis, based on numerical relativity strain data, demonstrates that the direct wave frequency is not correlated with the horizon frequency or surface gravity, except for an incidental crossing around a remnant spin $\chi_f \approx 0.7$, which coincides with the spin of the GW250114 event. Furthermore, it is observed that, although the instantaneous frequency of the direct wave is quasi-stable, its damping time shows significant evolution, invalidating models that assume a single damped sinusoid with a fixed damping time.

The authors also point out that evolving frequency models based on horizon properties fail to adequately describe the direct wave component for systems with large remnant spins. They conclude that attempting to verify Hawking's area law using a horizon frequency derived from the direct wave interpretation could lead to apparent violations of the law, even when no actual violation occurs. These findings suggest that the direct wave is not a reliable probe for investigating the horizon properties of black holes resulting from mergers.